Temperatures in the mid-20s on Tuesday left plants and autumn leaves on lawns sporting delicate lace-like trims, such as this one spotted in front of a home in Manteca early in the morning.

ROSE ALBANO RISSO/The Bulletin

There’s one important reason the oleander was the plant of choice for the median strip of Highway 99.

The beauty of their blossoms is obvious, but that reason is no more practical than the fact this perennial is not just drought-resistant but freeze-hardy as well.

Unfortunately, not so for the many equally attractive plants in the garden which need to be coddled from the cold when temperatures plummet to freezing points which had been the case in the last couple of days in these parts of the San Joaquin Valley. Ripon’s Park Greenhouse owner and plant expert Floyd Cover said the proverbial horse may already be out of the corral when it comes to the need to protect these precious delicate plants given the prevailing cold snap.

“It might be too late. It was 25 or 26 degrees this morning so the horse is out,” he said during a telephone interview on Tuesday.

But with some plants, he said, such as begonias, there’s a bit of hope left. “They freeze down but sometimes they come back up again,” Cover said.

One way to prevent your plants from being frozen when the temperatures dip to the 20s is to cover them, but never with plastic. Use burlap instead, he said.

“Plastic is not good (because) plastic is cold. Any fabric would be better than plastic because plastic transmits cold,” Cover said.The other important thing to keep in mind is to keep the plant soil moist, particularly container plants.

“We don’t like to have dry soil, even in winter,” Cover said. The reason: moist soil retains heat better than dry soil, for one thing, plus dry plants become more susceptible to damage.

Plants that “could be damaged now” because of the past few days’ freezing temperatures are “all your citrus trees and some of the bougainvilleas,” Cover said.

Citrus trees are evergreen, and usually these trees don’t freeze but they could lose their fruit to the freeze.

Tangerines, he said, are the most susceptible of these tree varieties simply because of their thin skin. But when your citrus fruits do get frozen in a cold snap, “you have a couple of weeks to use them before they lose all the juice, and they’re still good enough to eat,” Cover said.Longer than that and “they lose all the juice; sometimes they get rotten,” he said.

Here’s one way to find out if that citrus fruit is already a goner.

“Early in the morning around 9 o’clock, take a sharp knife and cut the fruit open. If you detect a bit of ice on the flesh, that means they’ve been damaged. If there’s a little bit of ice inside the skin next to the flesh, it’s still okay.”

If you’re looking for burlap materials to cover your cold-sensitive plants, they are available at just about every store that has a garden center or at a nursery like Park Greenhouse. Cover said they are currently out of the material, but he expects to receive additional shipments of this item in about six days. A garden employee at Orchard Supply and Hardware store in Manteca said Tuesday that they have still some of the burlap covers available.